The present invention relates generally to a Radio Frequency Identification (RFID) tag, and more particularly, to a technology for storing flag data representing a data processing state for a given time and restoring the flag data without an initialization process when power is temporarily turned off and then on while storing the flag data.
Generally, nonvolatile ferroelectric memory, i.e., Ferroelectric Random Access Memory (FeRAM), has a data processing speed similar to that of Dynamic Random Access Memory (DRAM). The FeRAM has been spotlighted as a next generation memory device whose data is conserved even after power is turned off.
An FeRAM device having a structure similar to that of a DRAM device includes capacitors made of a ferroelectric substance and has a high residual polarization allowing for data retention even after power is no longer supplied to the memory device.
An RFID device includes a reader automatically recognizing an object that is equipped with an electric tag using a radio frequency and reading information on the electric tag. The RFID device has been widely used in inventory control, supply chain management, and factory automation due to its fast recognition speed and large data storage capacity.
The RFID device includes a RFID reader and a RFID tag. The RFID reader includes an internal or external antenna. The antenna outputs an activating signal to form an electromagnetic field, i.e., a RF field. When a RFID tag enters the generated RF field, the RFID tag generates driving power for the RFID tag using the activating signal received from the antenna of the RFID reader and then transmits data stored in the tag to the RFID reader.
When there are a plurality of RFID tags in a read range of the RFID reader, i.e., within the generated RF field, the RFID reader is required to judge a data processing state for each RFID tag.
A conventional RFID tag receives a RF signal form the RFID reader to generate a driving power. When a power source is temporarily disconnected due to a change in location of the RFID tag or a change in the state of the RF signal, data (flag data) representing a current data processing state may be lost.
When this happens, it is impossible to judge which of the RFID tags is communicating with the RFID reader. When the power source is turned off and then on, the RFID tag initializes and processes data from the beginning. As a result, data processing speeds may be degraded and different new data may be processed even though the previous data processing was not finished.